Universal Knowledge Britannica?

I have a 23 volume set of Universal Knowledge Britannica, plus the index to volumes 1 to 23, an atlas with index, that has lists of contributors.

It is stored in its own wood book shelf with the large atlas that sits behind it. On the fourth page it has 1768 with a wild flower around the 1768. The front cover has 1769. They are cream books with red on the side.
Are they worth anything or should I throw them out?
Made in the USA.

By Petra